Patent application title: GAS BURNER WITH IMPROVED PRIMARY AIR DUCT

Abstract:

Gas burner, particularly for household cooking appliances, with an
horizontal or vertical gas supply conduit (1), a burner body with one
more flame crowns, an horizontal or vertical Venturi (4), a nozzle (5) to
inject the gas flow from said gas conduit into said Venturi pipe and,
means to provide the primary air flow which include a tubular conduit
which is coaxial and placed outside said gas conduit, and an opening to
allow the gas flow, placed between said nozzle and the inlet of the
Venturi pipe. The coaxial conduit draws the respective air flow from a
zone inside the body of said cooking appliance, and said opening allows
the passage of the respective primary air flow sucked and coming from
over the appliance top surface (12). In order to stir the primary air
flow passing through said coaxial conduit, a plurality of radial wings
(10A) is arranged, said wings being shaped either planar or helical, and
being connected on the outer surface of said gas supply conduit.

Claims:

1. Gas burner for cooking gas appliances, and particularly for household
cooking hobs, comprising:a burner body (2) on which one or more flame
crowns (3B, 3C) are mounted,a Venturi pipe (4),a gas conveying conduit
(1), extended on horizontal or on vertical, and terminating with a nozzle
(5) inside said burner body, apt of injecting the gas flow from said
conveying conduit (1) into said Venturi pipe (4),means to provide the
suction of the primary air flow, including two different inflow
paths:wherein a first path comprises a conduit (6), which is arranged
around said gas conveying conduit (1) and coaxial to it, forming a
prolonged annular interspace (7),and wherein the second path comprises a
through opening (8) arranged in a position downstream said nozzle (5) and
upstream the inlet to said Venturi pipe (4),said coaxial conduit (6)
being apt of drawing the relevant primary air flow from an inner zone of
said cooking appliance, said opening (8) being able of allowing the
intake of the respective primary air flow which is sucked and comes from
the upper zone of said cooking appliance, characterized in that:air
turbulating means are provided,able of stirring the primary air flow in
said coaxial conduit (6),and which are lodged inside said annular
interspace (7), extending from the outer surface of said gas conveying
conduit (1) to the inner surface of said coaxial conduit (6).

2. Gas burner according to claim 1, characterized in that said stirring
means comprise a plurality of wings (10), radially arranged with respect
to the axis (X) of said gas conduit (1),

3. Gas burner according to claim 1, characterized in that said stirring
means comprise a plurality of wings (10A), helicoidally arranged with
respect to the axis (X) of said gas conduit (1), and on the outer surface
(11) of it.

4. Gas burner according to claim 1, characterized in that said coaxial
conduit (6) is placed in correspondence to the end portion and around the
outer surface (11) of said gas conduit (1).

5. Gas burner according to claim 1, characterized in that said coaxial
conduit (6) and said Venturi pipe are horizontally oriented, and that
said coaxial conduit is provided with a prolongation (9) extending ahead
and towards said Venturi pipe (4) until substantially joining its inlet
mouth, and in that said through opening (8) is arranged in said
prolongation (9), said opening (8) being is placed in the upper portion
of said prolongation (9).

6. Gas burner according to claim 1, characterized in that said gas conduit
(1), said Venturi pipe (4) and said coaxial conduit (6) are vertically
oriented and are basically aligned, and that said through opening (8) is
made by a cylindrical or frustum-conical opening at 360.degree. having
its axis aligned or parallel to the axis of said Venturi pipe (4), and is
delimited on one side by the inlet mouth of said Venturi pipe (4) and on
the opposite side by said coaxial conduit.

7. Cooking appliance, particularly cooking hob, comprising a burner
according to one of the previous claims, characterized in that it is
provided with an upper plane or surface (12) which partially forms the
lower side of the suction inflow channel (13) of said second path and
which enters said through opening (8).

8. Cooking appliance according to claim 7, characterized in that the inlet
mouth (14) of said inflow channel (13) is arranged exactly over said
upper surface (12).

9. Cooking appliance according to claim 8, characterized in that in
correspondence to said inlet mouth (14), said upper plane (12) is being
formed with a relief shape (15).

10. Cooking appliance according to claim 9, characterized in that said
relief shape (14) is made up by working said upper plane (12).

Description:

[0001]The present invention relates to a gas burner, preferably of the
type generally used in the household cooking gas appliances and in
particular gas built-in hobs, provided with improved means to convey the
primary air into the Venturi pipe.

[0002]In the following of this description it will be referred to a gas
burner provided with both a central body with a peripheral flame crown,
and a perimetral body provided with two flame crowns, oriented inwards
and outwards, but it will be intended that what explained may be
identically applied and therefore valid also for gas burners provided
with only a peripheral body, that is without the central flame body.

[0003]It is known that in such kind of cooking gas appliance two main
requirements are present:

[0004]a constructional and assembly requirement, i.e. the cooking gas
appliance, particularly when it is a gas hob, has to show a minimum
height, due to constraints which are well known to the man skilled in the
art, and therefore will not be repeated, and

[0005]a functional requirement, consisting in that the burner, specially
those burners with limited diameter, are requested to provide in any case
a suitable thermal power, and in any case the maximum possible power.

[0006]These two requirements are however in apparent contradiction to each
other, as the need to keep down the total gas appliance height obliges to
also keep down the same height of the Venturi pipes providing the gas to
the burners; however such limitation operates also as a limitation for
the amount of gas/air mixture which can be produced, and therefore
determines the limit of the burner thermal power.

[0007]In order to overcome such reciprocal conditioning, some cooking
appliances have been proposed and divulged, which are provided with one
ore more Venturi pipes which are horizontally extended as for instance in
the patents WO 2005/078342 and WO 2007/012766.

[0008]It is apparent that by horizontally placing the Venturi pipes, it is
automatically void the problem of their height which conditions the
overall height of the cooking appliance.

[0009]Moreover the two cited patents show respective solutions wherein the
Venturi pipes leave from the burner central zone and branch out radially;
therefore their total length is limited by the radius, that is by the
horizontal size of the burner itself.

[0010]In order to eliminate such condition it was proposed, for instance
in EP Publication 1120603 and in EP Application n. 07119078.9 a type of
burner wherein the Venturi pipe is placed into horizontal for the whole
width, that is basically for the diameter of the burner body itself.

[0011]However the showed solutions suffer from a quite common drawback in
such type of burners, that is from the fact that the primary air is
sucked and sent to the inlet of the Venturi pipe from one access way
only, i.e. either from the inner box body of the cooking appliance, or
from the outer room, that is from the zone over the cooking hob itself.

[0012]Of course such circumstance does limit the total amount of the
available primary air, and therefore limits the available thermal power.

[0013]In order to increase the primary air inlet flow, it was proposed to
intake and convey the primary air flow through a coaxial and preferably
tubular conduit, the final portion of which ending with the gas injection
nozzle.

[0020]However no one of said patents suggest, and even less divulgates,
the solution which shows that the primary air flow, bound to the Venturi
pipe, is taken from two distinct access ways, that is from a conduit
which is coaxial to the gas conduit, and also from an opening which is
independent of said coaxial conduit.

[0021]It would therefore be desirable, and is actually a main purpose of
the present invention, to implement a kind of burner provided with two
different and distinct inlet ways for the primary air flows to the
Venturi pipe made up by a conduit which is coaxial to the gas conduit,
and by an opening or gate placed just after the gas injection nozzle,
wherein said access ways are independently flown with air taken from the
inside of the box body of the cooking appliance, and from the outer room
over it.

[0022]However such purpose turns to be profitable not only with gas
conduits and related Venturi pipes when horizontally oriented, where the
benefits are more apparent, but also with cooking appliances provided
with gas conduits and Venturi pipes which are vertically oriented, even
if some drawbacks may be experienced caused by the height of the cooking
appliance, yet the same the same benefits due to a double primary air
suction are achieved, i.e. from the inside of the cooking appliance body,
and from the outer room over it.

[0023]According to the present invention, this and further aims are
reached in a kind of burner provided with a Venturi pipe which can be
either horizontally or vertically extended, which is provided with
connecting and inlet conduits for the primary air flow incorporating the
characteristics as recited in the appended claims and including such
operating means as described below by mere way of non-limiting example
with reference to the accompanying drawings, in which:

[0024]FIG. 1 is a perspective outer view of a burner body and of the
relevant cooking gas appliance, here represented by a gas hob, according
to a first embodiment of the invention,

[0025]FIG. 2 is an exploded view of the cooking burner shown in FIG. 1,

[0026]FIG. 3 shows a vertical and side section view according to the
section A-A of the assembly of FIG. 1,

[0027]FIG. 3A shows a section view, which is orthogonal to the "X" axis of
the gas conduit, of a detail of the burner assembly of FIG. 3,

[0028]FIG. 4 shows a vertical and side section view according to the
section A-A of a different embodiment of the assembly of FIG. 1,

[0029]FIG. 4A shows a section view, which is orthogonal to the "X" axis of
the gas conduit, of a detail of the burner assembly of FIG. 4,

[0030]FIGS. 5 and 6 do show perspective views of the details respectively
shown in FIGS. 3A and 4A,

[0031]FIG. 7 shows a view which is equivalent to FIG. 3, but referred to a
cooking appliance provided with a gas conduit and a Venturi pipe which
are vertically oriented.

[0032]With reference to FIGS. 1 to 4, a cooking appliance according to the
invention comprises:

[0033]a gas supply conduit 1 horizontally oriented,

[0034]a burner body 2 on which one or more flame crowns 3B, 3C . . . are
mounted,

[0035]a Venturi pipe 4 which is also extended into horizontal, and is
substantially aligned with the final portion of said conduit 1,

[0036]an gas injection nozzle 5 at the end of said conduit 1 towards said
Venturi pipe 4.

[0037]The primary air is being conveyed towards said nozzle 5 and into
said Venturi pipe through two different flowing paths, i.e.:

[0038]the first path consists of a suction air flow beginning from inside
the body of the cooking appliance, and which in its end portion takes the
form of a conduit 6 coaxial with said first gas conduit 1, having a
preferably tubular shape, and which surrounds it at least in the end
portion; therefore between said gas conduit 1 and said coaxial conduit 6
a prolonged annular interspace 7 is formed, in which flows a share of the
primary air, sucked by the Venturi pipe.

[0039]As clearly shown in the figures, said coaxial conduit 6 stretches
towards said Venturi pipe 4, to which it joins through a suitable
prolongation 9; as a matter of facts, it may be observed that the Venturi
pipe is merely the properly shaped continuation of said prolongation 9,
which to its time stretches ahead beyond said injector 5;

[0040]the second path consists of a channel 13 whose suction mouth opens
over of the upper plane 12, and in its end portion a through opening 8 is
arranged, preferably placed on a side of said prolongation 9, just
downstream of said injector 5 and upstream of said Venturi pipe 4.

[0041]Said through opening 8 then allows the primary air flow to pass from
the outer room towards said Venturi pipe 4, so achieving the first
invention goal, i.e. to make the primary air to intake by splitting the
whole flow into two separate flows, one of which being arranged over said
upper plane 12, and the other being conveyed from the inside of the
cooking appliance and which in its end path enters into a conduit which
is coaxial to the gas conduit.

[0042]The just described solution allows some profitable improvements; the
first improvement consists in that, as shown in FIGS. 3 and 4, said
coaxial conduit 6 draws the relevant primary air flow directly from the
inner volume delimited by the box body 34 of the cooking appliance, while
instead said opening 8 is connected to the outer room, and exactly from
over its top surface.

[0043]This circumstance favors a better air flowing in the case that the
cooking appliance is undesirably lodged in such a way that the air
circulation is obstructed or slowed down; moreover the two primary air
flows, so conveyed, do not interfere in any working condition.

[0044]Also it is preferred that said opening 8 is placed upwards in said
prolongation 9, so as to shorten and to make straighter the path of that
share of primary air flow coming from over the cooking appliance.

[0045]Such solution is suitable to match the temperature increase; since
the heating from the burner reduces the density of the primary air, it is
important to improve the primary air flow, in order to avoid compromising
the burner functionality (combustion performances, yellow tipping and
soot).

[0046]In order to improve the mixing of the gas with the primary air, it
was experienced as an useful improvement to arrange some means able of
causing a turbulence in gas flow when coming out from the conduit 1, so
that the gas flow itself is being broken and therefore it is easier mixed
with the primary air flow.

[0047]It was then found profitable to arrange some suitable means able of
creating a turbulence in the air passing through said interspace 7, so
that the air going out from it, and basically from said coaxial conduit
6, is soon mixed both to the gas exiting from the conduit 1, and to the
primary air flow entering from said opening 8.

[0048]Such complete and prompt mixing effect both with the gas and with
the primary air flow obviously causes the mixture itself to become
optimized, what improves the combustion performances.

[0049]To this purpose, inside said interspace 7 and on the outer surface
11 of said gas conduit some stirring wings 10 are arranged; according to
the turbulence effect which is wanted, and also to the diameter of the
coaxial conduit 6 itself, the two following embodiments are proposed:

[0050]in the first embodiment and with ref. to the FIGS. 4 and 4A, said
wings 10 are flat, are preferably passing on the "X" axis of said gas
conduit 1, are radially oriented on the outer surface of the gas conduit
1, are regularly distributed at the same angular distance to each other,
and preferably are quite prolonged so as to be extended for the whole
length of said coaxial conduit 6.

[0051]in the second embodiment and with ref. to FIGS. 5 and 5A, said wings
10A are bent and specifically are placed in an helical arrangement, as a
screw thread, whose inner edge is still attached on the outer surface of
the gas conduit 1; said wings 10A too are regularly distributed with the
same angular distance, and preferably are quite prolonged so as to be
extended for the whole length of said coaxial conduit 6.

[0052]The two just described improved embodiments are obviously helpful to
make up a cooking appliance which is particularly effective not only from
the point of view of the thermal power supply, but also which is compact
and especially cheap and simple in the construction; moreover the
invention may be highly appreciated also due to the advantage that the
nozzle replacement may be carried out without any need to open the
appliance, as this operation may be performed across said opening 8.

[0053]As just described, the shown embodiments may be implemented by a gas
conduit and a Venturi pipe which are horizontally oriented, as
represented in the FIGS. 2, 3 and 4; however, as previously remembered,
it is also possible to make up the invention by placing the gas conduit
and the relevant Venturi pipe vertically oriented, as schematically shown
in FIG. 7.

[0054]In said case it has been proved that the most suitable embodiment,
both from a functional and a constructive point of view is offered by the
FIG. 7 itself, wherein said Venturi pipe is substantially separated from
the coaxial conduit 6 (differently from FIG. 3, wherein said devices are
interconnected by said prolongation 9).

[0055]Therefore the outlet mouth of the conduit 6 is completely opened,
and so the air path, coming from the outside and sucked into the channel
13, crosses an opening 20 showing a substantially cylindrical or
frustum-conical shape, extended on the horizontal plane for 360°,
and connecting the outlet mouth 6A of the coaxial conduit to the inlet
mouth 4B of the Venturi pipe 4.

[0056]Furthermore, and preferably, said same upper plane 12 makes also the
lower side of the channel 13 through which the primary air is sucked into
said second path and is conveyed into said opening 8.

[0057]So the inlet 14 of said channel 13 is then opened just over said
upper plane 12; moreover, in correspondence of said mouth 14 said surface
12 takes a profile in relief 15, so as the incidental liquids and cooking
remnants are prevented from entering said channel 13; advantageously said
relief profile 15 may easily be obtained by a proper pressing/bending
operation of this same upper plane 12.